Here are three books from the heart of what might be called climate alarmism. At least one of our authors - arguably the most scientifically respectable of them - wonders if the UN-sponsored Intergovernmental Panel on Climate Change isn't rather too timid. Fred Pearce puts the case that the official consensus-building body sticks to what is called "Type I" climate change. He reports the growing body of opinion supporting "Type II" climate change, which:

is much more abrupt and results from the crossing of hidden tipping points.

His book, then, is not an account of the official science and not all his laundry list of what he calls climatic monsters will find their way into the IPCC's hugely important update of its work due in 2007 (which will be as alarmist as it dare). Those of us who are sceptical of much of this process can't take much comfort from that: Pearce sticks only to evidence from people who can't be dismissed out of hand (though I am well short of abandoning my scepticism that they've got it all right). His particular hero is Jim Hansen ("President George W. Bush's top in-house climate modeller"), and Pearce's favourite argument is perhaps Hansen's view that the polar icecaps may melt much sooner and faster than the IPCC has hitherto thought likely.

That's scary enough, you might say. But there are plenty of other disasters which Pearce's sources expect.

Hurricanes, extreme weather, flooding, a giant "fart" of methane, the disappearance of the Amazon rainforest and a 20-metre rise in sea level are all supposed to be close to tipping points. We will return to whether any of this matters. For now it is worth noting that Pearce is doing no more than writing down the unvarnished opinions of some of the most senior and respected climate scientists on earth. He says very little in an authorial sort of way. His writing has a sort of hopeless larkiness about it -

You could say toodle-oo to Tuvalu by 2010

- but also an easy-going briskness which carries one along.

Al Gore's book is a much more interesting beast, and covers much the same territory. It goes about as far and no further than the Pearce, and is a fairly straight account of Mr Gore's film of the same title, which was itself supposed to be a fairly straightforward account of his famous slideshow. The film-makers apparently told Gore that his presentation needed juicing up a bit and so in both film and book we are served a rather odd account of his emotional state at two energising crisis points in his life. The bigger one was the near-fatal motor accident in 1989 which hospitalised his son. He writes:

I was handed not just a second chance, but an obligation to pay attention to what matters.

A bit later in the film and book he tells us about the death from lung cancer of his beloved sister (five years earlier) in 1984. This event plays into the emotional growth of Mr Gore in a rather different way. He uses it to tell us that the way the tobacco industry tried to persuade us that smoking was healthy is now replicated in some of the oil industry's campaigning against climate change alarmism. He also says he regrets his own family's commitment to tobacco farming which was only abandoned by Gore's father after his family tragedy. This is taken by Mr Gore to show that it takes a while for people to "join up the dots".

So he has it all ways: for at least twenty years his family grew a plant which was known to kill people, but that didn't matter morally too much because the naughty cigarette makers put up flak. Once bitten, he implies, he's in good shape to tell us to be quicker in making such judgements in spite of industry counter-pressure.

This guff is of a piece with his goofy essay (in the book) about his post-Vietnam wanderings in the wilderness. The hero abandons his worldly life. Like a St Francis, he knows the excitement of the temporal and has:

a healthy respect for the mesmerising power of an over-scheduled, overpopulated, hyperstimulated existence. It's designed to monopolise our attention, to sell us things….

Gordon Bennett, this could be Oliver James.

Al Gore has form as a self-obsessed, emotionally-clunky man in search of personal growth, of expiation and redemption. It featured heavily in his windy 1992 environmental testimony, Earth In the Balance. He has the curse of the Age of Aquarius: he yearns to be transformational. And why not? It doesn't necessarily damage and may enhance the way we think about his scientific quest and his desire to be useful. His book is mawkish, maybe. But oddly, watching him on film saying the same things is rather moving. This doesn't seem to be a Bill Clinton (nor yet a Tony Blair), working the audience as an actor might. Unless he's a very clever dissembler, this is a much odder business. At least one of his biographers, Bill Turque, seems both sharp and kindly when - in his Inventing Al Gore - he seems to endorse his subject's self-description as a person addicted to the main chance and to seriousness. It's the right kind of humbug to be, really.

We can now move to a book, Monbiot's, which takes as read the kind of climate alarmism argued-for in our first two. Monbiot is the Tony Benn of our day: a man whose heart and mind are firmly rooted in the instincts of the 17th Century Levellers. He begins with the premise that rich nations need to:

cut their greenhouse emissions by 90 per cent by 2030. This is the task whose feasibility "Heat" attempts to demonstrate.

This is going some: the UK government is not going to meet its "20 per cent by 2010" target and is now aiming at "60 per cent by 2050".

It is getting harder to know whether Monbiot is a romantic or a realist. He's sort of naïve: he wonders whose information to trust, as though these things were difficult and depended on finding out who's paying whom. He repeats at length Gore's analysis of the similarity of the tobacco and oil campaigns and their strategies. But he says:

feasibility... [means] compatibility with industrial civilisation.

This is a little odd in a man who is most famous for decrying that beast. Anyway, he runs through various technological options and - with a healthy scepticism about many of the most obviously "green" possibilities - concludes that we would need radically to change our ideas, for instance, about transport, to get anywhere close. He favours personal carbon quotas over "green taxes", as being less punitive for the poor (though they are actually likely to be hardly less so).

One can leave the details on the side, really. The big problem is that Monbiot mentions but takes no serious account of a much bigger problem for his argument and any like it. This is that the alarmist case (which he restates approvingly) is that at anything over 450 ppm (parts per million) of carbon equivalent in our atmosphere the chances are that the world's average temperature will rise somewhere between 2 and 3 degrees Celsius and unleash considerable and perhaps irreversible chaos. No-one serious seems to see any chance that we can avoid emissions of that order. (For elements of this view, hear the government's chief scientist, Professor Sir David King's contribution to the Radio 4's Today programme, 14th April, 2006.)

This view profoundly affects policy, though Monbiot in a way faces no real difficulty. He is at least partly a radical and probably wouldn't mind radical solutions. I'm inclined to agree with him at least to this extent: the amount of moving around we now do may well one day seem rather old-fashioned. Virtual travel may come to matter more to us. But however all that pans out, I am more concerned that Monbiot seems blithely indifferent to the gap between the small amount of action the world may well take and the large amount of action which he thinks it needs and ought to take. It seems especially useless to have that discussion unless one remembers the background he posits: that there will be climate chaos anyway.

The big question of course is this. If chaos is unleashed at present and unavoidable emission levels, how much chaos can be avoided by any plausible future reductions (or forced reductions in growth) in emissions? What will people say when they are told that it is too late to avoid chaos? And where is the pain-for-gain calculus? Will small amounts of policy produce usefully benign if small effects? If not, how on earth are we to persuade people to proceed to large amounts of policy?

Monbiot provides part of the answer, but doesn't enjoy or stress it. This is that politicians and public are now in a particular dance. Politicians know, as Monbiot says, that:

inside their electors there is a small but insistent voice asking them both to try and to fail.

These books may persuade waverers that there's trouble ahead, but they none of them address the more interesting policy question which itself hangs on the difficulty of making people accept pain for a gain which may be vanishingly small. Neither, come to that, does Sir Nicholas Stern, at least as evidenced by his 30th October Today programme broadcast announcing his review of the economics of climate change policy.